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Blomqvist, L., Berg, S. & Sandberg, D. (2019). Distortion in laminated veneer products exposed to relative-humidity variations: Experimental studies and finite-element modelling. BioResources, 14(2), 3768-3779
Open this publication in new window or tab >>Distortion in laminated veneer products exposed to relative-humidity variations: Experimental studies and finite-element modelling
2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 2, p. 3768-3779Article in journal (Refereed) Published
Abstract [en]

A shortcoming of the laminated bending process is that the product may become distorted after moulding. This study focused on the influence of fibre orientation deviation for individual veneers on the distortion of a moulded shell. The distortion of 90 cross-laminated shells of the same geometrical shape, consisting of seven peeled birch veneers, were studied under relative humidity variation. All the veneers were straight-grained in the longitudinal-tangential plane, but to simulate a deviation in fibre orientation, some of the individual veneers were oriented at an angle of 7° relative to the main orientation of the other veneers in the laminate. A finite element model (FEM) was applied to study the possibility of predicting the results of a practical experiment. The study confirms the well-known fact that deviation in fibre orientation influences shape stability. The results also show how the placement of the abnormal veneer influences the degree of distortion. From this basic knowledge, some improvements in the industrial production were suggested. However, the FE model significantly underestimated the results, according to the empirical experiment, and it did not show full coherence. The survey shows the complexity of modelling the behaviour of laminated veneer products under changing climate conditions and that there is a great need to improve the material and process data to achieve accurate simulations. Examples of such parameters that may lead to distortion are density, annual ring orientation in the cross section of the veneer, the orientation of the loose and tight sides of the veneer, and parameters related to the design of the moulding tool.

Place, publisher, year, edition, pages
North Carolina State Univ Dept Wood & Paper Sci, 2019
Keywords
Birch, Cup, FEM, Veneer, Wood, Twist
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-73340 (URN)10.15376/biores.14.2.3768-3779 (DOI)
Note

Validerad;2019;Nivå 2;2019-04-10 (oliekm)

Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-04-10Bibliographically approved
Gaff, M., Babiak, M., Kačík, F., Sandberg, D., Turčan, M., Hanzlíka, P. & Vondrová, V. (2019). Plasticity properties of thermally modified timber in bending: the effect of chemical changes during modification of European oak and Norway spruce.. Composites Part B: Engineering, 165, 613-625
Open this publication in new window or tab >>Plasticity properties of thermally modified timber in bending: the effect of chemical changes during modification of European oak and Norway spruce.
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2019 (English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 165, p. 613-625Article in journal (Refereed) Published
Abstract [en]

The plasticity of thermally modified European oak (Quercus robur L.) and f thermally modified Norway spruce (Picea abies Karst. (L.)) timber was evaluated in bending, and the plastic properties were related to the changes in chemical composition of the wood after modification. The objective was to gain new knowledge about the properties of materials in the plastic region of the force-deformation diagram in bending. A new software was developed (MATESS) and used to identify important characteristics of the material. This software eliminates shortcomings in current standards, such as simplifications in the evaluation of data when sufficiently sensitive measuring equipment is not available. The characteristics studied were: modulus of rupture (MOR), plastic potential (PP) chord modulus (CHM), the moduli of plasticity (EE), and the moduli of plasticity (EMV, EP). Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed chemically to reveal the patterns that occur during the loading of the specimens. Thermal modification has different effects on the mechanical properties of oak and spruce, especially on CHM, EMV and EP, due to their different contents and structures of their chemical components. A strong correlation (r > 0.90) between hemicellulose content and MOR and Pp values was found for both species. The coefficients of determination indicated a very low dependence (r2 < 0.1) of MOR, PP, CHM, EE, EMV and EP, on the average density.

Keywords
Chord modulus; Tangent modulus; Moduli of plasticity; Limit of proportionality; Middle value of plasticity; Modulus of rupture; Chemical analyses
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-72941 (URN)10.1016/j.compositesb.2019.02.019 (DOI)000462803100056 ()2-s2.0-85061626954 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-25 (inah)

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-04-17Bibliographically approved
Gaff, M., Kačík, F., Sandberg, D., Babiak, M., Turčani, M., Niemz, P. & Hanzlík, P. (2019). The effect of chemical changes during thermal modification of European oak and Norway spruce on elasticity properties. Composite structures, 220, 529-538
Open this publication in new window or tab >>The effect of chemical changes during thermal modification of European oak and Norway spruce on elasticity properties
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2019 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 220, p. 529-538Article in journal (Refereed) Published
Abstract [en]

The elasticity in bending of European oak (Quercus robur L.) and Norway spruce (Picea abies (L.) Karst.) timber was evaluated before and after thermal modificationand related to the changes in chemical composition of the wood as a result of the modification. A new software was developed (MATESS) and used to identify characteristic points on the force-deformation diagram. The modulus of elasticity(MOE), stress at the limit of proportionality (LOP) and elastic potential (PE) were used to describe the wood properties. Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed to reveal the patterns that occur during the loading of the specimens. Thermal modification lowers the mechanical properties (MOE, LOP and PE) of oak and spruce wood, and the reduction increases with increasing modification temperature. Changes in chemical composition of thermally modified wood show a strong relationship to the reduction in elasticity properties for bot species.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Modulus of elasticity, Limit of proportionality, Elastic potential, Thermally modified wood
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-73601 (URN)10.1016/j.compstruct.2019.04.034 (DOI)
Note

Validerad;2019;Nivå 2;2019-04-11 (johcin)

Available from: 2019-04-11 Created: 2019-04-11 Last updated: 2019-04-11Bibliographically approved
Markström, E., Kuzman, M. K., Bystedt, A. & Sandberg, D. (2019). Use of wood products in multi-storey residential buildings: views of Swedish actors and suggested measures for an increased use. Wood Material Science & Engineering
Open this publication in new window or tab >>Use of wood products in multi-storey residential buildings: views of Swedish actors and suggested measures for an increased use
2019 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed) Epub ahead of print
Abstract [en]

Many studies have shown that wooden buildings in general have a lower climate impact than buildings built of conventional materials such as concrete and steel. In Sweden, however, only about 10% of the multi-dwelling buildings are built with timber frames. The goal of this empirical study is to provide a broad picture of the views of Swedish actors regarding the use of wood products in multi-storey residential buildings and suggest measures for an increased use. A questionnaire concerning the use of wood products in construction was sent out to Swedish developers, main contractors, and architects and 100 answers were received. The study shows that the views of the groups of actors differ in some respects and factors that may either facilitate or be obstacles to an increased use of wood products were identified and discussed.

Keywords
Multi-storey buildings, wood products, Sweden, developers, main contractors, architects
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-73498 (URN)10.1080/17480272.2019.1600164 (DOI)
Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-04-08
Sandberg, D. (2018). Architects' perception of EWPs and modified wood in contemporary timber architecture. In: : . Paper presented at 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018.
Open this publication in new window or tab >>Architects' perception of EWPs and modified wood in contemporary timber architecture
2018 (English)Conference paper (Refereed)
Identifiers
urn:nbn:se:ltu:diva-72855 (URN)2-s2.0-85058164622 (Scopus ID)
Conference
2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018
Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12
Couceiro, J., Hansson, L., Ahec, A. & Sandberg, D. (2018). CT-scanning of the drying process of Eucalyptus nitens.. In: Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C., (Ed.), Proceedings of 21st International Drying Symposium.: . Paper presented at 21st International Drying Symposium, Valencia, Spain, Sep 11-14, 2018 (pp. 1269-1276). Valencia: Editorial Universitat Politècnica de València
Open this publication in new window or tab >>CT-scanning of the drying process of Eucalyptus nitens.
2018 (English)In: Proceedings of 21st International Drying Symposium. / [ed] Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C.,, Valencia: Editorial Universitat Politècnica de València , 2018, p. 1269-1276Conference paper, Published paper (Refereed)
Abstract [en]

The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research toimprove the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

Place, publisher, year, edition, pages
Valencia: Editorial Universitat Politècnica de València, 2018
Keywords
Cell collapse; computed tomography; surface checks; wood drying; internal checks
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71201 (URN)10.4995/ids2018.2018.7380 (DOI)978-84-9048-688-7 (ISBN)
Conference
21st International Drying Symposium, Valencia, Spain, Sep 11-14, 2018
Available from: 2018-10-13 Created: 2018-10-13 Last updated: 2019-01-15Bibliographically approved
Couceiro, J., Hansson, L., Sehlstedt-Persson, M. & Sandberg, D. (2018). CT-studies during the Conditioning phase of the Wood Drying Process. In: : . Paper presented at 21st International Drying Symposium (IDS), Valencia, Spain, Sep 11-14, 2018.
Open this publication in new window or tab >>CT-studies during the Conditioning phase of the Wood Drying Process
2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Computed tomography (CT) during drying of sawn timber is an excellent non-destructivetechnique to study the moisture flux as a function of drying time. In this study, a climatechamber combined with a medical CT- scanner has been used for non-destructive studies ofdensity changes in sawn timber during drying and conditioning.Green sawn timber contains large amounts of water and has to be dried before it can befurther processed and used in various building applications. The most common dryingmethod is convective air-circulation drying in large industrial kilns, where the relativehumidity (RH) of the hot circulating air is gradually reduced until the timber reaches thetarget moisture content (MC).Drying of sawn timber is driven by the existence of a difference in MC between the coreand the surface, so that moisture moves from the wet inner region towards the drier outerregion. During the early capillary stages of drying, the drying rate is high while, at the laterstages when all liquid water has evaporated, the drying rate is slow and diffusioncontrolled.At the end of the drying process, the timber surface is always drier than its core.In addition to this moisture gradient, internal stresses develop within the cross section withcompression stresses in the timber surface and tension in the inner regions. To avoidunwanted distortions, both these stresses and the moisture gradient, need to be eliminatedbefore the timber is further processed. This is achieved in a final conditioning stage withinthe drying process by moistening the circulating air through steaming or water spraying.The aim of the present work was to optimize the conditioning stage by developing amethod for studying of moisture gradients, deformations and internal and externaldimensional changes in sawn timber during the conditioning phase by using a CT-scannercombined with a drying unit for in-situ measurements of moisture flow.The results show that it is possible to detect the moisture gradient between the surface andcore of the timber with satisfactory reliability, but not the internal and external dimensionalchanges. However, this method creates a potential for increasing the knowledge andunderstanding of the conditioning phase and makes it possible to optimize and develop thisstep in the drying process to improve the yield and ensure a higher quality of the sawntimber.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71117 (URN)
Conference
21st International Drying Symposium (IDS), Valencia, Spain, Sep 11-14, 2018
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2019-01-15Bibliographically approved
Myronycheva, O., Karlsson, O., Sehlstedt-Persson, M., Öhman, M. & Sandberg, D. (2018). Distribution of low-molecular lipophilic extractives beneath the surface of air- and kiln-dried Scots pine sapwood boards. PLoS ONE, 13(10), Article ID e0204212.
Open this publication in new window or tab >>Distribution of low-molecular lipophilic extractives beneath the surface of air- and kiln-dried Scots pine sapwood boards
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2018 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 10, article id e0204212Article in journal (Refereed) Published
Abstract [en]

During industrial wood drying, extractives migrate towards the wood surfaces and make the material more susceptible to photo/biodegradation. The present work provides information about the distribution, quantity and nature of lipophilic substances beneath the surface in air- and kiln-dried Scots pine (Pinus sylvestris L.) sapwood boards. Samples were taken from knot-free sapwood surfaces and the composition of lipophilic extractives, phenols and low-molecular fatty/resin acids layers at different nominal depths below the surface was studied gravimetrically, by UV-spectrometry and by gas chromatography-mass spectrometry (GC-MS). The concentration of total extractives was significantly higher in kiln-dried than in air-dried samples and was higher close to the surface than in the layers beneath. The scatter in the values for the lipophilic extractives was high in both drying types, being highest for linoleic acid and slightly lower for palmitic, oleic and stearic acids. The amount of fatty acids was low in kiln-dried boards, probably due to a stronger degradation due to the high temperature employed. The most abundant resin acid was dehydroabietic acid followed by pimaric, isopimaric, and abietic acids in both drying types. It is concluded that during kiln-drying a migration front is created at a depth of 0.25 mm with a thickness of about 0.5 mm.

Place, publisher, year, edition, pages
PLOS, 2018
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71200 (URN)10.1371/journal.pone.0204212 (DOI)000446921100033 ()30303988 (PubMedID)2-s2.0-85054716404 (Scopus ID)
Projects
Experimental studies of capillary phenomena in bio-based materialsFungal growth on modified wood-based products under subarctic conditionsModWoodLifeUnderstanding wood modification through an integrated scientific and environmental impact approach
Funder
Swedish Research Council
Note

Validerad;2018;Nivå 2;2018-10-29 (svasva)

Available from: 2018-10-13 Created: 2018-10-13 Last updated: 2018-10-29Bibliographically approved
Trischler, J., Sandberg, D. & Dorn, M. (2018). Effect of temperature during vital gluten adhesive preparation and application on shear-bond strength. Journal of Adhesion Science and Technology, 32(4), 448-455
Open this publication in new window or tab >>Effect of temperature during vital gluten adhesive preparation and application on shear-bond strength
2018 (English)In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 32, no 4, p. 448-455Article in journal (Refereed) Published
Abstract [en]

If protein-based adhesives are to become a competitive bio-based alternative to synthetic adhesives, the preparation and application methods have to be considerable improved to reduce process time and thereby improve the economy of the adhesive system. The purpose of this study was to investigate the impact of the temperature during preparation and application on the shear-bond strength of an adhesive based on vital gluten for use in wood applications. Vital gluten was used in its natural form and mixed with water of different temperatures (preparation temperature 0 °C or 20 °C), and applied on beech veneer at different temperature (application temperature –10, 20, 60 and 100 °C). Tensile shear-bond strength samples were prepared and tested according to EN 205. The results showed that an increase in veneer temperature during application of the adhesive led to a decrease in the shear-bond strength, but that the preparation temperature of the adhesive had no influence on the strength.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-64983 (URN)10.1080/01694243.2017.1362807 (DOI)000419353700009 ()2-s2.0-85027024483 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-29 (rokbeg)

Available from: 2017-08-09 Created: 2017-08-09 Last updated: 2018-01-23Bibliographically approved
Myronycheva, O., Sehlstedt-Persson, M., Karlsson, O. & Sandberg, D. (2018). Growth of mold and rot fungi on copper-impregnated Scots pine sapwood: Influence of planing depth and inoculation pattern.. BioResources, 13(4), 8787-8801
Open this publication in new window or tab >>Growth of mold and rot fungi on copper-impregnated Scots pine sapwood: Influence of planing depth and inoculation pattern.
2018 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, no 4, p. 8787-8801Article in journal (Refereed) Published
Abstract [en]

The biocidal properties of an industrially used copper-based preservative were evaluated at different planing depths on exposure of pine wood to mold fungi in direct and indirect contamination methods, with simultaneous verification of white rot fungi virulence on wood. The preservative was an aqueous solution of copper carbonate, 2-aminoethanol, and quaternary ammonium compounds. Full cell preservative impregnation efficiency against visual mold fungi growth was tested on sapwood surfaces planed to different depths before impregnation. The virulence of two white rot fungal strains of Trametes versicolor (441 and JPEI) against the dried non-impregnated and impregnated wood samples was also tested. The unplaned surface of impregnated timber was occupied by air-borne contaminants, such as Paecilomyces variottiand Aspergillus niger up to 30%, and, even after impregnation it was necessary to process the surface to avoid micro-fungi settlement. The virulence of the tested rot fungi strains was confirmed by the aggressive degradation of non-impregnated wood with a mass loss of over 40%. Both Trametes sp. strains degraded the preservative-impregnated wood with a mass loss of 3.1% to 4.8%, but degradation by the JPEI strain was more intensive and more dependent on planing depth than the other strain (441).

Place, publisher, year, edition, pages
North Carolina State University, 2018
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71285 (URN)10.15376/biores.13.4.8787-8801 (DOI)000454215100118 ()2-s2.0-85056570471 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-30 (svasva)

Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2019-01-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4526-9391

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